Process of making soap



Sept. 27, 1949. v B. CLAYTON 2,483,002

PROCESS OF MAKING SOAP Filed Dec. l11, 194s Patented Sept. 27, 1949 Benjamin Clayton, San Marino, Calif., assignor y Y to Benjamin Clayton, doing business as Refining, Unincorporated Application December 11, 1946, Serial No. 715,564

4 Claims. (Cl. 260-417) This invention relates to a process of making soap and more particularly, to a high temperature process of saponifying glycerides in which a neutral or somewhat alkaline soap is produced while minimizing the destruction of glycerine.

In high temperature processes of making soap and recovering glycerine by vaporization thereof frommolten anhydrous soap, it has been difficult to produce a high quality soapk while avoiding excessive destruction of glycerine. Caustic alkalies have been considered necessary for the saponication of glycerides as it is known that non-caustic alkaline compounds, such as alkali metal carbonates, do not saponify glycerides to any appreciable extent or that the reaction is so slow as to render the process impracticable in conventional soap making processes in which the temperatures employed do not greatly exceed the boiling point of water. In fact soda ash and other so-called non-saponifying alkalies such as trisodium phosphate, cli-sodium phosphate, etc., have been employed or suggested as neutralizing agents for the fatty acids in the rening of vegetable oils because of their inertness to glycerides in order to prevent or minimize saponication of glycerides.

of the fatty acids of the glycerides into soap, i. e., f

insufficient to produce a neutral soap, the soap is of poor quality due to the thermal decomposition of the unsaponied fatty material at the high temperatures existing in the process. The pro- "duction of a neutral soap in such a process using caustic alkali as the saponifying agent requires a small excess of the alkali over that theoretically required to combine with the fatty acids of the glycerides. 'At the high temperatures employed a small amount of the alkali combines with im` f purities inthe glycerides which do not react with alkali in conventional soap making processes or in conventional tests tol determine the saponication number of the fatty material. Caustic alkaliy in excess, will react with glycerine when the latter is volatilized under the conditions prevailing in the vapor separating chamber. The latter two reactions proceed along with the main reaction of the alkali with the fatty, acids liberatrecovery of glycerine is substantially less than the theoretical recovery even when the small amount of glycerine which remains in undecomposed form in the soap is taken intoy consideration. Proportioning apparatus has been developed to a high degree of accuracy such that a neutral soap can be consistently produced but even the production of a neutral soap results in substantial destruction of glycerine.

Also, a small amount of free or unreacted alkali is usually desirable inthe iinished soap and in some cases a strongly alkaline soap is desired containing a relatively large amount of free alkali. The most satisfactory manner of uniformly distributing this alkali throughout the soap is to add the alkali during the saponifying reaction. This additional excess alkali also acts to destroy glycerine if added in the form of caustic alkali.

In accordance with the present invention I have found that under the conditions existing Vin such high temperature processes, non-caustic alkalies, such ras alkaline `compounds, of alkali metals, can be substituted for a part of the caustic alkali while still carrying the saponfcation reaction to completion. Such non-caustic alkalies do not react as rapidly as caustic alkalies but they also do not decompose glycerine to an extent approaching that of caustic alkali even at the high temperatures employed. A neutral soap or a soap containing a substantial excess of alkali can be produced While minimizing destruction of glycerine. The major portion of the saponifying agent may still be caustic alkali but the amount yof suchrcaustic alkali is less than that required to react lwith'the fatty acids of the glycerides. The caustic alkali reactsmore rapidly with the this reaction as well as that furnishing any excess Vfor other reactions or any free alkali in the finished. soap is substantially all non-caustic alkali. The preferred operation is, therefore, to use somewhat less caustic alkali than necessary to saponify the glycerides in conjunction with suflicient non-caustic alkali to complete the saponication of the glycerides and furnish a small excess of alkali. By this process a high quality soap of high detergent qualities can be produced with negligible destruction of glycerine.

I have further found that the non-caustic alkali may consist entirelyv or partially of soda ash even though carbon'dioxide is liberated in the reaction between the soda ash and the fatty acids split from the glyceride molecule. By operating the process so that carbon dioxide has an 'ed from the glyeerides with the result that the 55 opportunity to Separate from the reaction mass.

the reaction can be carried to substantial completion. The high Vacuum desirable for Vaporizing glycerine from the soap does effectively remove the cabon dioxide from the reaction mass and, in general, the vacuum pumps usually employed in the vacuum system are adequate to discharge the carbon dioxide from the system although carbon dioxideeabsorptionin .the vacuumsystem maybe employed, yif necessary. k.Soda ash` is the preferred alkali for completing the reaction and furnish any desired excess alkali in the present inventio-n as it is relatively inexpensive and also modies the characteristics of the heated-soapv'to render the glycerine more easily .distilled from the soap. Substantially complete 'vaporization :fof glycerine can be accomplished even without rendering molten the resulting anhydrous soap, thus enabling a powdered anhydrous lsoap"to"b'e^`dire'ctly produced.

It is, therefore, an object of the present inven- .tion to .provide .animproved process of saponify- .ingglycerides with alkali under high temperature conditions .in whichglycerine is separated .from the :soap by Avaporization Athereof while .minimizin-g destruction of .glycerine Another `object of .the .invention is yto-provide .a .high .temperature rapid .process of -saponify- .ing fglycerides .-with alkali in which .at least ya portion of `the .alkaliis of the .ty-De .which mini- ;.mizesrthedestruction of glycerine.

A..f.urther object of the .invention is .to .provide an .improved processor saponifying .glycerides in which van excess of .an .alkali .which minimizes the .destruction of .glycerine `is .-employed -under .high 'temperature conditions.

.Astill further object of theinvention is to pro- .vide an improved process of saponifyingglycerides and recovering `glycerine in which agreaterrecovery-.of glycerine is accomplished and a ypowdered .anhydrous soap ldirectly produced.

Other objects and advantagesof-.the invention =will appear in the following description -of a 4preferredembodiment ofthe invention .made in connection Ywith the attachedA drawing `which .il lus Atrates.anapparatus suitable for carrying out the `present invention.

.Referringto the drawing, the apparatus may include a source of `supplysuch .asatank `I0 .for saponiiiable material-and a source of supplysuch :as `a -tank v|| for'saponifying agent. rIn ,accord- :ance with the `present invention -the Asaponiable `material may'consist essentially 4of glycerides f or ymaybe a'mixture of fatty `or other saponifable :acids .and .glycer-ides. The s-aponifying agent is preferably .predominantly a caustic alkali ad- .mixed with a small .amount of anfalkaline com- :pound 'of an. alkali metal, forV example soda ash, butwif an insoluble soap is desired the saponify- .ing agent vmay `include an alkaline earth metal `hydroxide -or alkaline compound thereof. The .saponirlable material may befwithdrawn vfrom the =tankf|i3 by mean-s cfa pump l2 and forcedthrough -a theat exchanger vI3 which may be of any suitable `type capable of :rapidly heating a flowing stream and preferably comprises a coil i4 through which the material torbe heatedis passed and a `casing |.5 through which any suitable heating pressure drop ,the equipment.

electric motor I9 with a speed change device 2| positioned between the pumps |2 and although any suitable proportioning mechanism may be employed preferably that shown in the patent to Thurman No. 2,142,062 granted December 27, 1938. mixer I6 is preferably a ow mixer of the type also disclosed in said patent, but may be anysuitable type of mixer 'suchvas a closed mechanical agitator.A The resulting mixture from the mixer I6 is preferably passed through another heat exchanger 22 wherein the temperature of the mixture is further raised and then passed through Yanother vpump 23 which serves as an additional .mixingdeviceaswell as helping to overcome the The mixture .from .the pump 23 is then preferably passed throughanother heat exchanger 24 and delivered into 'a vapor separating chamber 26.

.Thevapor separating chamber 25 is preferably provided with a lower conical portion 2'1' pro- .vided with a .lower inlcined wall against `which the .mixture from the heat exchanger 24 is directed by aplurality ofnozzles '28. The lower 'con- 'ber`26 against entranceof air. The .casing .31| .of

therscrew conveyor .may be provided Withacooling jacket-3'. through which vany/desired .cooling medium such as .water.may.be circulated.

.The vapor separating.chambert` .may be :provided with a .condensersystem Aincluding acon- -denser 38 connected to the vapor .separating chamberf .through apipe .39, a receiver 4| .connected to .the condenser 38, a condenser 42 connected to the receiver 4|, and ..a.receiver 43 connected to the condenser 42. .If soda `ash or other carbonate .is employed -as part of the .saponifying agent a vcarbon .dioxide absorbing -chamber 44 .may be connected to .thereceiver A3, betweensuch receiver and a Vacuum pump IAE .to reduce the vload on'the vacuum pump. The-carbon dioxide absorbing tower 44 .may 4be of .any suitable type such as a bubble tower 4.through which is passed a suitable carbon vdioxide absorbing liquid. The preferredfabsorbing liquid is 4a.solution .of caustic soda'which reacts .with the carbon dioxideltoform sodium carbonate, The resulting-sodium carbonate solution may be employed as part of the saponifyingagent.or-sold .asa .product of commence. Otlher .absorbing liquids Asuch as hydroxides .ofother alkali or alkaline earth metals or certain .amines or ethanolamines may, -however, be used as .the carbon dioxide absorbing agent.

In thepreferred operation of the present inventionforprorlucing a sodiuml soap the saponiable material is substantially all glyceride oil or f at although. it may .contain substantial quantities .of free fatty acids. Thergreater theproportion of glycerides-employed `in the saponiiiable material the greater the glycerine recovery. The saponifying agent is preferably arelatively concentrated aqueous solutionof caustic` sodacontaining sui- .cientsoda-ash to minimize destruction of glycervthan 1% based on the total weight `of alkali and in no case has commercial caustic soda sold for soap making processes been encountered in which the soda ash or other non-saponifying alkali present in the caustic soda even approached 2%. .Caustic soda containing 2% soda ash and obtained by deliberately adding soda ash to commercial caustic soda to bring the soda ash content to this amount has no .appreciable effect in reducing glycerine destruction in high temperature soap making operations. Caustic soda containing 5% of soda ash does, however, in all cases encountered reduce the destruction of glycerine to a very small amount, i.l e., to an amount appreaching that which laboratory. experiments have shown should result if no caustic sodar were present. This amount of 5% has, therefore, been adopted in commercial operations in accordance with the present invention. No precise lower limit on the effective amount of soda ash applicable to all glycerides or glyceride fatty mixtures can be given as the minimum amount of soda ash usable in a given case depends to a large extent uponthe nature of the fatty material being saponiiied, for example, the amount'of materials other than fatty acids and glycerine whichwill react with alkali under the conditions of operation. In most cases 3% soda ash will minimize glycerine destruction and sometimes even less is sufficient. In all cases more than 2% is required.

As to the upper limit of soda ash, 10% is in most cases a practical upper limit. Addition of soda ash in amounts greater than 5% have no substantial effect in further reducingv destruction of glycerine and increase'the amount of carbon dioxide which must be discharged from the vacuum system. Also, soda ash tends toprecipitate out of concentrated caustic soda solution, for eX- ample 25 B. solutions when added in amounts above By reducing the concentration `of the caustic soda solution, however, .amounts of soda ash as great as 25% of the total alkali can be employed. While the proportions of the noncaustic to caustic alkali have been discussedparticularly with respect to caustic alkali and'soda ash, these proportions are, in general, applicable to other non-caustic alkalies as well as other caustic alkalies.

The proportions of saponiable material to total alkali are initially calculated from the saponication number of the saponiable material by known formulas. Since the saponication number of the saponiable material is determined at low temperatures, more alkali than indicated by such determination is required at high temperatures to produce a neutral soap because of yreactions with impurities present and with .a small amount of glycerine. For a neutral soap this additional alkali will vary with the nature of the saponiable material but will usually be less than 1% based on the amount of saponiiiable material. alkali is added. This further alkali may range from 1/2 to 3% and should'be non-caustic alkali particularly if the total alkali which is just su'icient to produce Ya neutral `soap contains approximately the smallest amount of non-caustic alkali which will. minimize glycerine destruction. The important consideration is that the caustic alkali be more than 2% and preferably 3% to 5% less ..65 If an alkaline soap is desired, further 'v remainder of the alkalibeing non-caustic alkali. That is, there should be enough non-caustic alkali present to'minimize attack on the glycerine by the alkali. e

.Both the saponifiable material and saponifying agent aref preferably preheated in heat exchangers i 3 and I8, respectively', to relatively high temperatures; For example, Vthe saponifiable material'may be heated to temperatures between300 and 450 F. Becausev of the corrosive nature of the alkaliit may be desirable to preheat this material t0 a somewhat lower temperature, for example 200 to 300, although with corrosion resistant materials in the heat exchanger and pipe lines this temperature may be substantially the same as that for the saponifiable material. The temperature of the resulting mixture in the mixer i5 may therefore range between 300 and 450 F. and temperatures in the upper range are preferable. Y

In general, it is desirable to maintain su'icient pressure in the preheating heat-exchangers I3 and i8, the mixer l0, and the heat exchanger 22 to' prevent any substantial vaporization of water although liberation of carbon dioxide may take place in the heat exchanger Z2. The caustic alkali reacts rapidly with the glycerides to liberate glycerine and produce soap. At the temperatures maintained in the heat exchanger'22 substantially no destruction of glycerine by the caustic alkali is produced and even though the temperatures in the Aheat exchanger 22 are suiiciently high to cause caustic alkali to decompose glycerine, the caustic alkali reacts with the glycerides at a suiciently rapid rate that it is consumed before substantial destruction of glycerine is pr duced. Sufficient soda ash likewise reacts with the glycerides in the heat exchanger 22 to substantially carry the s-aponication reaction to completion and a substantial amount of carbon dioxide lis generated. This substantially completely saponied mixture is then preferably passed J through another heat exchanger 24 in which the pressure is somewhat lowered and if necessary additional heat supplied to the mixture. Thus temperatures of the mixture leaving the heat exchanger22 may be between 400 and 475Y F. `while the temperature of the mixture leaving the heat exchanger 2Q may range between approximately 450 and 650 F. andis usually substantially above 500F. The pressure in the heat exchanger 24 is preferably made sufficiently low that substantial amounts of water vapor are liberated therein and smalll amounts of carbon f dioxide which might restrain the saponication reaction due to the law of mass action are likewise liberated. Thus a mixture of gases, vapors and soap containing a small amount of excess soda ash is discharged into thevapor separating ychamber Z5. Allof the caustic alkali is rapidly used up in saponifying the glycerides so that the excess of alkali is substantially all soda ash.

The mixture delivered vinto the vapor separating chamber 25 may he at suiciently high temperature to render the soap moltenafter glycerine and water vapor have been removed therefrom. However, the presence of the excess soda ash raises the melting point of the soap so that the soap containing excess soda ash can be recovered in powdered form after the glycerine and .water vapors have been separated therefrom. It has been found that substantially neutral soap or even soap containing a small amount of unreacted glycerides or fatty acids or unreacted caustic than that required to produce a neutral soap, the ,.1115 SodaA $119111@ Pe' 0f` h igh enugl lit; Hll312ll'u lfeSr t0 ansa-'co2 .heinzmoltenzform afterithevapors have desenfreairoved itherefrom :if .substantially `complete lseparationz-oiiglycerine vapors istoLbe obtained. 'in accordance with the present invention, v'it has .further vfound that :when a Aportion of the saponiiication is accomplished withfsodaashland excess/soda ash remains iin the soap, glycerine and 'Water 'vapors 4are substantially completely "removed l:from vthe .soap -feven though Y'the "soap is not of sufhcently high temperature to be rin molten `form afterthe vapors lhave been' removed therefrom. 'Thus temperatures in the vapor-'separating-chamber may 'bexas low as 450 Fxwhi'le .still obtaining substantially complete separation anrrglycerine vapors, or maybe-as'hi'gh asf600 -orll'iigher'without destruction of glycerine while still 'producing ahigh quality soap. Byfcorrelating the-excess vamountfoi soda ash with the temperature'andvacuum employed `inthe vvapor separating :chamber a substantially dry powdered soap A.vvl'iicll does-.not fadhereto the 'chamber walls or scrapermechanism 'can be pro duced with substantially complete separation ol yglycerine vapor.

This soap may Ybe discharged from the 'vapor separating :chamber @by 'means 'of the rscrevv conveyor and cooled during rdischarge below a .temperaturelatwhichft Willbe damaged by con- :tact with the atmosphere. Suche temperature is in-theneighborhood'of 4120F. Also,'water may be Aintroduced `Into 'the conveyor chamber 34 through .i-'a piped? v.to assist' in Acooling the soap vor to cool :and -fhydrate'thersoap to any desired degree prior 'to discharge from 'the :conveyor The screw conveyor :maybe vor the type "shown inthe .Thurman Patent No. 2,'l90;615:granted 'February -1, 19`i0,:andtwo ortmorefconveyors may fbe used .in series,if desired.

vapors are iwithdrawn'from the vapor'separating chamber 2.5 throughthe pipe 39 'atta rate `suii- `ciently high to produce a relatively high hvacuum in the "vapor separating chamber, "for exampley a vacuum of at least28l/2 "to 29 inchesf'of'mercury. By lemploying a series of condensers'such'as the condensers 38 and `lM, glycerine and Water vapors may be fractionally condensed. Thus a concentrated solution lof glycerine or substantially pure glycerine may be Withdrawn from 'the receiver 'M :and the 'Water Icondensed in `'the condenser '42 and 'Withdrawn `from the receiver t3. ncondensible gases, which maybe lsubstantially fall carbon "dioxide, if soda'ash is iusedzin'the process, may fthen be -passed'through :the carbon'dioxide 'absorber'ill and'any remaining gases exhausted'fromthe systenrby the vacuum pump E6.

It has been "found that glycerine destruction by caustic alkalies, for example caustic soda, becomes relatively rapid in the neighborhood of 500 F. For example, heating Va solution containing 20% glycerine and 2.5% sodium hydroxide, under pressure to prevent evaporation, to I500 F. in fifteen minutes and then rapidly cooling, results 'in the destruction of approximately 2% of the glycerine. The amount of glycerine destroyed doubles for approximately each '25 F. increase in temperature above 500 F. Where the heating in each case is carried out in fteen minutes. The amount of vdestruction of glycerine increases substantially proportional to the concentration of sodium hydroxide and it also increases substantially proportional to the time at which the mixture is maintained at agiven temperature. It has also been found .thatthe `presence of soap in the solution'has substantially no effect upon the rate of glycerine destruction. It will thus be seen that the presence of any Asubstantial excess o 8 licxaius'tic ialkali in -ithe :reaction ymixture containingfglycerineaatf temperatures above approximate- 15T-500 results ,infa substantial destruction of glycerine.

-On `the other ih'and, fit has .been foundzunder the same/conditions o'f temperature, concentration, etc., that the fdestruction of glycerine by soda ash is :approximately Y'one-terrtlri of the vdestructionofglycerineby-causticsoda Byemploying -less fcaustic "soda than vthat necessary 'to saponify the glyceride-and supplying the remaining alkali aswell asi-arr excess inthe I'form of A,soda ash, :the "high ftemperature Jsaponifi'cation may be carried on with negligiblefdes'truction of 'glyccrine even ithough temperatures substantial-ly above 500 F. `are employed. The -time during which vthe Kmaterials in 'the `process "are 'subjected to 1high temperatures is extremely small. Also, if apowdered.anhydroussoap is desired theprocess can b e carried on at temperatures below 550 While'at the same time securing substantiallycompleterecovery of glycerine.

As .a .specific example of rthezpresent process, a glyceride .containing .approximately .10% combinedglycerineon the basis ofthe total fat was saponiied .in accordance Awith 4the present .invention .employing Aa nal vtemperature .of ap- `preitimately 550.'E. 'The alkaliemployed was an aQueous-:caustic soda solutioncontaining `,5..% soda ash ron :the basis Yof the total valkali `and having a concentration of -25 B. -4at .room ...temperature The yproportions of alkaliand. saponiable A.materialfwere .adjusted-so that the `resulting soap Was slightly 1alkaline. .The I^glycerine :recovered by vaponlzation and :condensation vwas 9% roi `the @total -fat and-0.\75% glyeerine-fonthesame basis was lleft ybehind -in the soap. Thus-.0.25170 .glycerine was destroyed yor f on .the `'basis .of lthe total glycerine2:51%A wasl destroyed. When-causticisoda alone iis 'gemployedmnder thesa-me conditions to produce "a soap having lthe same alkalinity, the `destruction tof `'glyct-:rine iis approximately '25% or .ten @times 4as great. "While soda .ash is 4the preferrednon-Lcaustic alkali' because: of ritsfcheapness .zand availability and ,modification :of vthe propertiesoffthe resultant. soap, `other non-caustic alkali'es-"suchas other alkaline salts may beemployed, gfor example ldii-sodium phosphate or 5trisodiumphosphate to-gve substantially the same results.

This application is a continuation-impart of my 'copending"application Serial `No.-'435,'679, ltiled MarchZl, `19212 which has now become abandoned.

EWhile I have disclosed-the preferred embodiment of :my invention, Ait is understood that the details thereof may be varied Withinthe scope of i the following claims.

I claim:

1. ,Ahigh'teInperature,process of making soap and recovering glycerine, Which comprises, reacting a "fatty.materialconsisting essentially of glycerides of '.fatty acids with. a mixture of caustic and .non-caustic alkali in `an amount .at least 66 suficientto-.completely react with said fattymaterial, saidmixture beingfessentially caustic alkali with a :minor .amount Yof non-.causticalkalL .the amount ,of caustic alkali beingsnbstantiallyfless than .that necessary .to completely react Withsaid l fatty material and the amount Yof Anon-caustic alkali being loetweenapproximately 3% ,and 10% ofthe total alkali and su'flicient to minimize destruction of,.glycerine at the temperature of reaction, completing said reaction .ata temperature 76 atleast as'ligh as 450F., and separating glyc- Y erine in Vapor form under vacuum conditions from the reaction mass.

2. A high temperature process of making soap and recovering glycerine, which comprises, re-

acting a fatty material consisting essentially of glycerides of fatty acids with a mixture of caustic and non-caustic alkali in an amount at least sufficient to completely react with said fatty ma-V high as 450 F., and separating glycerine in vapor Y form under vacuum conditions from the reaction mass.

3. A high temperature process of making soap and recovering glycerine, which comprises, reacting a fatty material consisting essentially of glycerides of fatty acids with a mixture of caustic and non-caustic alkali in an amount at least sufcient to completely react with said fatty material, said mixture being essentially caustic alkali with a minor amount of non-caustic alkali, the amount of caustic alkali being between approximately 90% and 97% of that necessary to produce a neutral soap, the remainder of the alkali being noncaustic alkali in an amount at least sufficient to produce said neutral soap, completing said reaction at a temperature at least as high as 450 F.,

1oand separating glycerine in Vapor form under vacuum conditions from the reaction mass.

4. A high temperature process of making soap and recovering glycerine, which comprises, reacting a fatty material consisting essentially of glycerides of fatty acids with a mixture ofV caustic and non-caustic alkali in an amount at least sufficient to completely react with said fatty material, said mixture being essentially caustic soda with a minor amount of soda ash, the amount of Vcaustic soda being between approximately 90% and 97% of that necessary to produce a neutral soap, the remainder of the alkali being soda ash in an amount at least sufficient to produce said neutral soap, completing said reaction at a temperature betweenapproximately 500 and 650 F., and separating glycerine in Vapor form under YVacuum conditions from the reaction mass.

Y BENJAMIN CLAYTON.

REFERENCES CITED The following references are of record in the file of this patent:

Y UNITED STATES PATENTS VCTI-IER REFERENCES VTheMerck Index, Ed. 5, 1940, page 512.

Dedication 2,483,002-Benjamz'n @Zag/ton, San Marino, Calif. PROCESS 0F MAKING SOAP.

Patent dated Sept. 27, 1949. Dedication led June 30, 1964, by

t e assignee, Benjamin Olaf/t0n, doing business as Reym'ng, Uninoorpomted.

Hereby dedieates to the publie the terminal part of the term of said patent effective December 31, 1963.

[Oficial Gazette September 2.9, 1964.] 

